Klippel-Feil Sequence Health Article

Definition

Individuals with Klippel-Feil sequence (KFS) were originally described as having a classic triad of webbed neck (very short neck), low hairline, and decreased flexibility of the neck. More commonly, abnormal joining or fusion of two or more vertebrae (bones) of the cervical spine (neck bones) characterizes Klippel-Feil sequence.

Description

Klippel-Feil sequence is extensive fusion of multiple cervical vertebrae (the uppermost bones of the spine). There may be complete fusion or multiple irregular bony segments in the bones of the upper back (cervical and often upper thoracic spine). Premature and extensive arthritis and osseous (bony) spurring affecting the joints of the spine (facet joints) are common in individuals with Klippel-Feil sequence.

There are three classifications of Klippel-Feil sequence.

• Group 1 exhibits fusion of the lower skull (head) and the first bone of the spine (the first cervical vertebrae (C1)). The second and third spinal bones (cervical vertebrae C2 and C3) are also usually fused together in Group 1. The normal cervical spine has seven bones or vertebrae. Normally half of the ability of humans to bend their heads forward (flexion) and backwards (extension) occurs in the joints between the base of the skull and the uppermost spinal bone. The other half of the motions of flexion and extension occur in the rest of the upper spine. Therefore, the danger is due to the excessive motion of the neck between the joints that are fused.
• Group 2 has fusion of bones (vertebrae) below the second cervical bone (C2). Group 2 also has an abnormal skull and upper spinal bone connection.
• Group 3 has an open space between two fused segments of spinal bones.

Genetic profile

Although this is usually a sporadic occurrence, an abnormal gene responsible for Klippel-Feil sequence has been found on the q (long) arm of chromosome 8. The human cell contains 46 chromosomes arranged in 23 pairs. Most of the genes in the two chromosomes of each pair are identical or almost identical with each other. However, with KFS individuals, there appears to be a reversal or inversion on part of chromosome 8.

Demographics

Approximately one out of every 42,000 people has Klippel-Feil sequence. The classic triad is seen in 52% of individuals with the syndrome. Men and women are affected equally, however, some studies have shown slightly higher numbers for women. There have been some reports of Klippel-Feil sequence being more common among infants born with fetal alcohol syndrome (FAS) because FAS affects bone development of the fetus. However, there is a genetic component that passes the syndrome on through the generations in a dominant inheritance pattern.

Signs and symptoms

The first clinical signs are the classic triad of webbed neck, low hairline, and decreased flexibility of the neck. However, the presence of abnormalities of the cervical spine found with x rays is the hallmark diagnosis. Other signs and symptoms may be found, but vary from person to person.

Some patients may exhibit wryneck or Torticollis, which is a twisting of the neck to one side that results in abnormal carriage of the head. The individual may have differences between the two sides of his face, known as facial asymmetry. Patients may also have scoliosis (abnormal curves of the spine).

A variety of miscellaneous abnormalities may clinically manifest themselves in Klippel-Feil sequence. Deafness occurs in about 30% of the cases. Ear abnormalities such as very small ear lobes (microtia), or deformed bones within the ear (ossicles) may be present. They may even have a small or absent internal ear.

Abnormalities of the blood vessels such as a missing radial artery in the forearm may decrease the size of the thumbs (thenar hypoplasia). Anomalies of the right subclavian artery (artery under the clavicle or collar bone) have been reported as well as higher incidences of artery anomalies of the upper neck (cervical vertebrae). Anomalies of the genital areas and urinary system are also common.

Individuals diagnosed with Klippel-Feil sequence frequently have problems with cervical nerves and nerves that go from the neck to the arms and hands. Individuals can have pain that starts in their neck and travels into the arms if the nerve roots coming off of the spinal cord are irritated or pinched.

Diagnosis

Klippel-Feil syndrome is usually diagnosed in early childhood or adolescence. Observing the clinical signs of having the classic triad of webbed neck, low hairline, and limited cervical ranges of motion initiates the diagnosis. When further testing is done such as x ray, the diagnosis is confirmed by the fusion of multiple cervical vertebrae.